New Zealand women are tweeting selfies wearing lipstick because the nation's new opposition leader, Jacinda Ardern, was asked by a male leader of a minority party to prove she was "more than lipstick on a pig".

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Jacinda Ardern.

Opportunities Party founder Gareth Morgan made the comment during a Twitter conversation about whether the popularity of NZ Labour's new leader was a distraction from policy.

"Jacinda should be required to show she's more than lipstick on a pig," he tweeted.

"'Putting lipstick on a pig' is a euphemism for a meaningless face lift or makeover," he wrote. "And until such a time that we see real change from the Labour Party we think that the euphemism is appropriate."

Prime minister Bill English condemned Morgan's description as "deliberately appalling", but Ardern said she was "not particularly bothered by it".

Earlier this month, just hours after Ardern was unanimously elected leader of her party, she was asked by a TV host about whether she had made a decision between "having babies and having a career".

The next morning, co-host of The AM Show Mark Richardson asked her whether New Zealanders had a right to know whether a potential prime minister might take maternity leave.

“It is totally unacceptable in 2017 to say that women should have to answer that question in the workplace, it is unacceptable, it is unacceptable," Ardern told Richardson.